Tuning of the pitch height of thermotropic cellulose esters

Titelangaben

Hou, Haoqing ; Reuning, Arndt ; Wendorff, Joachim H. ; Greiner, Andreas:
Tuning of the pitch height of thermotropic cellulose esters.
In: Macromolecular Chemistry and Physics. Bd. 201 (2000) Heft 15 . - S. 2050-2054.
ISSN 1521-3935
DOI: https://doi.org/10.1002/1521-3935(20001001)201:15<2050::AID-MACP2050>3.0.CO;2-I

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Abstract

Butyric esters of (2-hydroxypropyl) cellulose (BuPC) with different degree of substitution(DS) were synthesized via control of the esterification time of butyryl chloride and (2-hydroxypropyl) cellulose. These BuPCs are thermotropic and displayed different colors at ambient temperature due to the formation of a cholesteric structure and the occurrence of a corresponding cholesteric reflection. The pitch height was found to increase significantly with a decrease of the degree of substitution. Both the glass transition temperature and the melting temperature are not affected by variation of the DS. The BuPC samples displayed a banded texture or focal-conic texture, respectively. The X-ray diffraction studies revealed the presence of a layer structure. The cl-spacing between two adjacent layers in the cholesteric structure displayed no significant dependence on the DS in the range from 2 to 3.